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September, 1909 and has been used with the most completely satisfactory re- apparently sults. There are scores of ships with quadruple and four-crank 'triple en- gines in which no attempt has been made at balancing, which are also per- fectly satisfactory. But none are free from disturbance under certain condi- tions, and it is also tree that in the most aggravated case v-bration is ab- sent under certain conditions. This 'by way of introduction to a discussion of the deductions in Prof. Henderson's paper in the June Review. This: appears to us to be an ex- treme case of endeavoring to make facts fit a preconceived theory and at the same time show why they do not; thus proving the case either way. It is moreover based on fallacious as- sumpt'ons, as where he says, "In ships the amplitude of vibration is, as a rule, negligible, unless there is approx- Attention has been called time and again to se- imate equality in the period." vere cases in ships without machinery at - all, and consequently no _ regular- ity of per.od. It how- the consistently view that supports, which has been by. the. Rue frequent- We be- lieve that we cannot insist too often ever, doctrine advanced the ly responsible for vibration. propeller is that of remediable d*sturbances the chief, and practically all of any conse- quence, are due to the propeller. If a fraction of the study and care given to the subject of balancing were given to the propeller, we would hear less of vibration. : The turbine' was to have relieved both builders and travelers of all an- noyance in this respect, thanks to the enthusiasm of the uninformed, among whom may be classed many owners and managers who were, and are still, possessed by the that the Sne was at the root of all disturb- ance. As a matter of fact, however, the turbine thas only succeeded in pointing out the necessity of seeking other explanations, and in the absence idea en- of reciprocating or rotative unbalanced weights the propeller has been ar- taigned as the criminal, and while it is undoubtedly with a greater measure of respons:bility than any other cause, it is by no means chargeable TAE MarRINE REVIEW responsible solely even in turbine The trim of the ship, stowage of weights, ships, as is sought to be shown. water ballast, weather, speed, all have their effect on any given ship, and no known type of motor or system of balancing or form of propeller will meet all conditions successfully. Prof. Henderson draws deductions based on treating the shp as a bar inherent harmonic with consequent characteristics. Any degree of famil- iarity with ships would seem to have prohibited such an assumption. Every weights change in distribution of must change the characteristics. A change in cut-offs without any change in weights or revolutions will do the same thing. On a long voyage the burning out of the bunkers will bring about. a changes: as a matter. of. fact there is no such thing as formulating a law on the subject, or framing rules which will apply under any two vary- ing conditions. Prof. Henderson is quite convinced that the for everything, which we do not dis- law of 'harmonics accounts pute, since any conceivable case will surely 'be found to be explained by some one or other of his hypotheses. But what we want is some way of determining beforehand what is to be expected with reasonable certainty and how to meet the condition; not to explain it afterwards, and we maintain that at present that knowlege is ab- solutely wanting. Analyzing impulses and disturbances after they occur and after it is too late to bring things to accord with a guesswork theory may be interesting as a study, but it is in- conclusive and without: pract'cal value. Not the slightest evidence is yet forth- coming that anyone's theory or system his ever prevented or cured a case of vibration, instances are abun- dant of their failure. Where there is one ship fitted on any systein run- ning smoothly, there are fifty with no doing equally -- well. while system at all Neither system nor lack of it meets all condit-ons. Careful construction and ajustment of the propeller will do more than anything else to prevent vibration, 'but if any owner expects that the adoption of turbines or any 337. empirical "system" will insure absence of vibration, he is misled. THE STATUS OF THE TURBINE. Elsewhere will be found an abstract of a paper contributed by Prof. Ira N. Hollis -- zine, to the Enginecring the movement of 'the recently clamorous Prof. Hollis, though for some years connected with Maga- which emphasizes vearward turbine advocates. lal- Harvard University, is not without both ashore, having reached the grade of marine experience, afloat and chief enginéer in the Unted States navy before going to Harvard. We invite attention to the relative propeller efficiencies which Prof. Hol- lis quotes from the acceptance trials of United States cruisers. We are ac- customed to hear claims of superior economy in coal consumption per horsepower advanced on behalf of 'the although forthcom'ng the slightest evidence in turbine, there is not yet support of this as regards marine in-_ stallations. We may yet be perfectly willing to concede a large gain in fuel economy per horsepower without in any way detracting from the superior efficiency of the reciprocating engine, - For instance, take the figures for the Birmingham, Salem and Chester at 2214 knots and compare the slip per- centages. It will be seen that the sl'p percentages 'are almost 50 per cent higher for the turbine than for the reciprocating engine. It would re- quire a very considerable gain in steam economy to even counterbal- ance the falling off in propeller ef- It will be seen that at all speeds the the Birmingham are immensely supe- ficiency. propeller efficiencies of rior to both the Salem and Chester. The vibration question appears in a new light, but we are disposed to think that very few will agree with Prof. Hollis' on this point. So far as commercial applica- conclusions tions are concerned, we think the question of vibration will cut a very large figure, and the recent experi- ence of the Mauretania and Lusitan'a is a case in point. The turbine is in its proper place in the naval ship and in the high speed passenger ship, but if its adop-